Electrical conductor coated with a blend of a polyester and an aminotriazine-aldehyde resin



United States Patent 3,338,743 ELECTRICAL CONDUCTOR COATED WITH A BLEND OF A POLYESTER AND AN AMINO- TRIAZINE-ALDEHYDE RESIN Deno Laganis, Schenectady, N.Y., assignor to Schenectady Chemicals, Inc., Schenectady, N.Y., a corporation of New York No Drawing. Filed Oct. 8, 1963, Ser. No. 314,633

11 Claims. (Cl. 117-218) The present invention relates to an oil-free, heat-resistant electrical insulating varnish.

In commercial practice today electrical wires, e.g., the magnet wires of an electric motor, are coated with a wire enamel. The enamel coated wire assembly is then dipped into an insulating varnish and the varnish set on the coated wire.

Recently there have been developed wire enamels which are in the Class H category (suitable for continuous use at 180 C. or above). One such wire enamel is Isonel 200 which can be used at 190 C. and above.

Unfortunately, most insulating varnishes are not suitable for use at such high temperatures. Thus, conventional oil-modified alkyd resins and polyesters have heretofore been limited to insulating varnishes for armatures and field coils of motors operating at Class B temperatures or, at best, at Class F temperatures (155 C.). Typical of the better oil-modified alkyd insulating varnishes which are suitable for Class F use are those in Thielking Patent 3,080,331.

Alkyd resins containing only a small amount of oil or fatty acids, e.g., 5 to 20% have poor thermal stability for a prolonged period of time.

Until the present time only silicone insulating varnishes have withstood the extreme high temperature conditions required for a Class H category. However, silicone varnishes are expensive and are not readily adaptable for all uses. A

A common test for measuring the temperature resistance of wire enamels and varnishes is the dielectric twist aging test described in Thielking on col. 5, lines 57-63. In general, the higher the temperature of testing the shorter the time before failure. In the dielectric twist aging test it has been found that the time before failure gives a straight line graph when plotted logarithmically against '80,000 hours at 205 C. and an infinite life at lower temperatures. In contrast, a commercial Class F enamel had a life of 70 hours at 260 C., a life of 240 hours at 240 C., a life of 3000 hours at 205 C., a life of 80,000 hours at 160 C., and an infinite life at lower temperatures.

It is an object of the present invention to provide an insulating varnish having improved high temperature properties.

Another object is to prepare an insulating varnish suitable for application over Class H wire enamels.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those isophthalic or terephthalic polyester with a small amount of an alkylated triazine aldehyde resin.

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A triazine-aldehyde resin is used in an amount of 2 to 20% of the total weight of polyester and triazinealdehyde by weight. Preferably, 5 to 15% of the triazinealdehyde resin is employed.

As the triazine there can be used benzoguanamine, formoguanamine, acetoguanamine, lauroguanamine, stearoguanamide, propioguanamine, melamine or any of the triazines ,set forth in Widmer Patent 2,197,357. Preferably, the triazine is a guanamine, most preferably benzoguanamine. The alkylated benzoguanamine-aldehy-de resins have been found to have better flexibility and heat resistance than the corresponding alkylated melamine-aldehyde resins. While there can be employed various aldehydes such as formaldehyde, acetaldehyde, propionaldehyde and furfural the preferred aldehyde is formaldehyde.

As the alkylating agent there can be used methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, secondary butyl alcohol, amyl alcohol, hexyl alcohol, cyclohexyl alcohol, octyl alcohol, isoctyl alcohol, 2-ethylhexanol. The preferred alcohol is butyl alcohol. With methyl alcohol there has been observed a tendency to blister.

The preferred resin is butylated benzoguanamineformaldehyde. Other suitable triazine resins include methylated benzoguanamine formaldehyde, ethylated benzoguanamine formaldehyde, propylated benzoguanamine formaldehyde, sec butylated benzoguanamineformaldehyde, amylated benzoguanamine-formaldehyde, cyclohexylated benzoguanamine-formaldehyde, octylated benzoguanamine formaldehyde, isooctylated benzoguanamine-formaldehyde, butylated benzoguanamine-acetaldehyde, butylated benzoguanamine-furfural, amylated formoguanamine formaldehyde, hexylated acetoguanamine-formaldehyde, butylated acetoguanamine-formaldehy de butylated lauroguanamine-formaldehyde, heptylated stearoguanamine-formaldehyde, butylated melamineformaldehyde, butylated N,N-dimethyl melamine-formaldehyde. As the polyester there is employed the reaction product of a mixture of a polyhydric alcohol having at least three hydroxyl groups such as glycerine, trimethyloletha-ne (TME), trimethylolpropane (TMP), pentaerythritol, tris(2 hydroxyethyl)isocyanurate, dipentaerythritol, tripentaerythritol, 2,4,6 hexanetriol, alpha methyl gluco side, and sorbitol and a diol such as ethylene glycol, propylene glycol, but'ylene glycol, 2,2,4-trimethyl pentanediol, neopentyl glycol, diethylene glycol, dipropyle-ne glycol, butanediol 1,4, pentanediol 1,5, di(hydroxymethyl) ether of diphenylolpropane (bisphenol-A-ethylene oxide adduct) or butenediol-1,4 with isophthalic acid or terephthalic or the acyl halides thereof, e.g., isophthalic acid dichloride, or a lower 'dialkyl ester thereof, e.g., methyl, ethyl, propyl, butyl, amyl, hexyl and octyl isophthalates and the corresponding terephthalates, as well as the half esters, e.g., monomethyl isophthalate. Orthophthalic acid is unsuitable since its polyesters depolymerize and deesterify at high temperature. The preferred diol is neopentyl glycol and the preferred alcohols having at least three hydroxyl groups are glycerine, TME and TMP.

While there can be employed of the polyhydric alcohol ester of terephthalic acid or isophthalic acid, preferably, the acid component is partially replaced by aliphatic dibasic acids to provide improved flexibility to the polymer chain or backbone during heat aging. The addi tion of the aliphatic dibasic acid overcomes the deficiency of cracking or development of minute fissures in the film coated on the wire during the elevated temperature aging period. As the aliphatic dibasic acid there is preferably employed adipic acid, but there can also be used succinic acid, glutaric acid, pirnelic acid, malonic acid, azelaic acid and sebacic acid.

'On a molar basis there is normally used 1 mol of diol to from 0.7 to 5 mols of polyhydric alcohol having at least three hydroxyl groups. On an equivalent basis there is used 1 mol of diol to from 1 to 7.5 equivalents of polyhydric alcohol having at least three hydroxyl groups. Preferably, there is 1.6 to 5.5 equivalents of the polyhydric alcohol having at least three hydroxyl groups per equivalent of diol.

The total number of hydroxyl groups on the alcohol reactants is usually from 1 to 1.7 times the total number of carboxyl groups of the acids. Preferably, the hydroxyl groups are 1.4 to 1.6 times the carboxyl groups.

When an aliphatic acid is employed generally there is used from to 60 mol percent of aliphatic dibasic acid and 80 to 40% of isophthalic acid or terephthalic acid. Preferably, to mol percent of the acid component is to aliphatic dibasic acid.

The preferred polyester of the present invention is the neopentyl glycol-glycerine mixed ester of isophthalic acid and adipic acid.

The resins of the insulating varnishes of the present invention are heat reactive. The insulating varnishes can be used to coat copper wire or motor rotors made of magnet wire directly but are usually employed over an enameled magnet wire.

The preferred enamel is the polymeric ester of a polycarboxylic acid of the group consisting of terephthalic acid and isophthalic acid with up to 80 equivalent percent of another polycarboxylic acid, e.g., adipic acid, hemimellitic acid, succinic acid, sebacic acid, hexachloroendomethylene tetrahydrophthalic acid or the like, and an alcohol of the group consisting of tris(2-hydroxyethyl)isocyanurate with up to 90 equivalent percent of another polyhydric alcohol, e.g., any of the diols or polyhydric alcohols having at least three hydroxyl groups set forth previously. The total number of hydroxyl groups on the alcohol reactant is from 1 to 1.6 times the total number of canboxylic groups of the acid.

The preferred enamel is a Class H enamel. Examples of the preferred enamel are those made from the following compositions, the parts all being by weight.

Composition A Parts Ethylene glycol 147 Glycerine 97 1,4-b-utanediol 74 Tris(2-hydroxyethyl)isocyanurate 608 Dimethyl terephthalate 1164 Composition B Parts 2,2,4-tetramethyl 1,3-cycl0butanediol 119.6

Tris (Z-hydroxyethyl) isocyanurate 5 1 1 Ethylene glycol 129 Glycerine 128 Dimethyl terephthalate 1112.8

Composition C Parts Tris(2-hydroxyethyl)isocyanurate 1044 Dimethyl terephthalate 776 Composition D Parts Tris(2-hydroxyethyl)isocyanurate 992.

Ethylene glycol 88 Dimethyl terephthalate 920 Composition E Parts Tris(2-hydroxyethyl)isocyanurate 556 Dimethyl terephthalate 413 Adipic acid 31 cal 4 Composition F Parts Tris(2-hydroxyethyl)isocyanurate 4400 Ethylene glycol 481 Dimethyl terephthalate 5019 Composition F is a wire enamel available commercially as Isonel 200.

The wire enamels from Compositions A, B, C, D, E and F are not a part of the present invention but can be made in the manner set forth in Meyer et al. application Ser. No. 117,499, filed June 16, 1961.

The insulating varnishes of the present invention include conventional solvents such as aromatic hydrocarbons, e.g., xylene, benzene, toluene, aromatic naphtha, aliphatic hydrocarbons, e.g., hexane cyclohexa'ne, petroleum ether, aliphatic naphtha, octane, mineral spirits. Generally, the solvent also includes an oxygenated solvent such as butyl alcohol, a myl alcohol, ethylene glycol monoethyl ether (Cellosolve), ethyl glycol monomethyl ether acetate (Methyl Cellosolve Acetate), diethylene glycol monoacetate, ethylene glycol, capryl alcohol, ethyl alcohol, dioxane, isophorone, acetone, butyl carbitol diisobutyl ketone, butyl acetate methyl ethyl ketone. Also, there can be used N-methyl pyrrolidone, tetrachloroethylene, or dimethyl formamide as a solvent. Usually, 25 to 75% by weight of the solvent is an aromatic hydrocanbon and the balance (75 to 25%) is an alcohol.

Unless otherwise indicated in the following examples all parts and percentages are by weight. Uformite MX-61 is a commercially available butylated benzoguanamineformaldehyde resin containing 60% solids in butanolxylene (1:1).

Example 1 208 grams of neopentyl glycol were charged to a reaction vessel equipped with an agitator, thermometer, inert gas sparge tube, and a Snyder fractionating column having a distilling head, thermometer and condenser attached thereto. With carbon dioxide sparging through, the glycol was heated to a temperature of 220 to 260 F. until it was completely liquefied. Then, 432 grams of trimethylolethane, 465 grams of isophthalic acid and 175 grams of adipic acid were charged to the flask. The resultant mixture was then rapidly heated until distillate evolved. The head temperature of the column was controlled at 200 to 210 F. The temperature of the batch itself gradually :rose from 300 to 450 F. After to of the theoretical water of esterification was collected to the contents of the reaction vessel were rapidly cooled to 350 F.

At this point the remaining ingredients were added, namely, 384 grams of trimethylolpropane, 465 grams of isophthalic acid and grams of adipic acid. Heat was again applied and the mixture reacted until an acid number of below 20 was obtained and the viscosity was H-V at 50% solids in a 1:1 xylene-butanol solution. The reaction product was then cooled to 300 F. and a 1:1 xylene-butanol mixture added to give a final product having a viscosity (Gardner-Holdt), 77 F. of Zl /z, acid number 10.2 and 54.9% solids. The ratio of the reactants used in Example 1 was as follows:

Neopentyl glycol-4 equivalents: 2 mols Trimethylolethane-20.4 equivalents: 6.8 mols Isophthalic acid1l.2 equivalents: 5.6 mols A-dipic acid4.8 equivalents: 2.4 mols Example 2 Employing the same apparatus as in Example 1 there were charged into the reaction vessel 478 grams of neopentyl glycol. The glycol was heated at 220 to 260 F. until it was completely liquefied.

The remaining reactants were added in three increments. First, 234 grams of adipic acid and 332 grams of isophthalic acid were charged into the reaction vessel and heated and the mixture heated gradually from 300 to 450 F. After 90 to 95% of the theoretical water of ,este-rification was collected the contents of the reaction vessel were rapidly cooled to 350 F.

'At this point the second increment of material was added, namely, 475 grams of glycerine (96%), 175 grams of adipic acid and 266 grams of isophthalic acid. The mixture was again heated to 350 to 450 F. The reaction was carried on until 90 to 95 of the theoretical water of esterification was collected, The batch was then cooled to 350 F.

The third and final increment, namely, 266 grams of isophthalic acid was then added and the temperature of the mixture raised to 370 to 450 F. The mixture was reacted until an acid number below 20 was obtained, and the viscosity was L-X at 65% solids in a solvent blend of xylenezn-butanol (butyl alcohol) in a 3 :1 ratio.

The reaction product was cooled to below 300 F. and mixed with a solvent blend of xylenezn-butanol (3:1) to form a solution having a viscosity (Gardner-Holdt), 77 F. of V /z, acid number 7.7 and 66.6% solids.

The ratio of the reactants used in Example 2 was:

Neopentyl glycol9.l2 equivalents: 4.56 mols Glycerine (96%)-14.88 equivalents: 4.9 6 mols Isophthalic acid10.40 equivalents: 5.20 mols Adipic acid5.60 equivalents: 2. 80 mols Example 3 90 parts of the polyester product of Example 1 at 54.9% solids (non-volatiles) were mixed at room temperature with 5.4 parts of the nbutan-ol, 5.4 parts of the xylene and parts of 'Uformite MX-61 to produce an insulating varnish. Based on the total solids, the polyester was '89.1 8% and the benzoguanamine resin 10.82%.

Example 4 85 parts of the polyester product of Example 1 at 54.9% solids (non-volatiles) were mixed at room temperature with 5.7 par-ts of the n-butyl alcohol, 5.7 parts of xylene and parts of Uformite MX-61 to produce an insulating varnish. Based on the total solids, the polyester was 83.83% and the benzoguanamine resin 16 .17%.

Example 5 405 parts of the polyester product of Example 2 at 66.6% non-volatiles were mixed at room temperature with 45 parts of 'Uformite MX-6l and 66 parts of methyl Cellosolve acetate (methyl ether of ethylene glycol monoacetate) to produce an insulating varnish. Based on the total solids, the polyester was 90.9% and the benzoguanamine resin 9.1%.

Example 6 467.5 parts of the polyester product of Example 2 at 66.6% non-volatiles were mixed at room temperature with 82.5 parts of Uformite MX-61 and 66 parts of methyl Cellosol-ve acetate to produce an insulating varnish. Based on the total solids, the polyester was 86.28% and the benzoguanamine resin 13.72%.

The varnishes of Examples 3 to 6 were suitable for directly coating copper wire, motor rotors, motor stators, armature and field coils of motors and the like, but are especially useful when applied over magnet wires (or other wires) coated with a Class H wire enamel such as Isonel 200. In Table 1 there are given the results of the use of the insulating varnishes of the present invention.

In Table 1 the Twisted Pairs test was carried out by employing No. 18 magnet wire enameled with Isonel 200 and twisted '9 twists in 4.75 lengths using a 3 pound tension on the pairs. There was then applied two coats of varnish reverse dip and each coat was first prebaked at 200 F. for 1 hour and cured for 1 hour at 200 C. The specimens were then aged at 260 C. and 1000 volts electric pressure wire applied from time to time until failure occurred. This test is the standard AIEE No. 57 Heat Life Test.

In Table 1 the Glass Cloth test was that of the standard MIL-I-2707B June 14, 1961 specification whereby a 3 mil glass tape of 1.5 inches in width and 8 inches in length was given two coats of varnish reverse dip, and each coat prebaked for 1 hour at 200 F. and cured for 1 hour at 200 C.

5 specimens of coated cloth tape of each example were taken and aged at 250 C. for 7 days (16-8 hours). After this testing period the samples were cooled to 23 C. and 50% relative humidity for approximately 1 hour. 5 unaged specimens were also chosen and were conditioned for 7 days at 23 C. and 50% relative humidity.

In the Twisted Pairs test the varnish of Example 3 would have a life of 7000 hours at 240 C., a life of 50,000 hours at 205 C. and an infinite life at 190 C. The varnish of Example 4 also would have an infinite life at 190 C. The varnishes of Examples 5 and 6 also would have an infinite life at 180 C.

What is claimed is:

1. A copper electrode coated with the cured mixture of an insulating varnish including (1) a curable oil-free alkyd resin selected from the group consisting of the esters'of reactants consisting essentially of a plurality of polyhydric alcohols with a member of the group consisting of isophthalic acid, terephthalic acid and mixtures of such acids with up to 60% of an aliphatic dicarboxylic acid, at least one of said polyhydric alcohols containing only two hydroxyl groups, the sole polyhydric alcohol containing only 2 hydroxyl groups being at least one member of the group consisting of propylene glycol, butylene glycol, 2,2,4-trimethyl pentanediol,, ne-opentyl glycol, diethylene glycol, dipropylene glycol, butanediol-L4, pentanediol-1,5 and butenediol-1,4 and at least one of the polyhydric alcohols containing at least three hydroxyl groups there being 0.7 to 5 mols of alcohol containing at least 3 hydroxyl groups for each mol of polyhydric alcohol containing only 2 hydroxyl groups and there being 1.4-1.6 hydroxyl groups in the reacting alcohols for each carboxyl group in the carboxylic acid and (2) from 5 to 15% of a curable alkylated aminotriazinc-aldehyde resin based on the total weight of the alkyd resin and the alkylated aminotriazine resin.

2. A coated conductor according to claim 1 wherein the aliphatic dicarboxylic acid is a saturated hydrocarbon dicarboxylic acid containing 4 to 10 carbon atoms, and the alkyl group of the alkylated aminotriazine-aldehyde has 1 to 8 carbon atoms and the aldehyde is formaldehyde.

3. A coated conductor according to claim 2 wherein the aminot-riazine is a guanamine.

4. A coated electrical conductor according to claim 3 wherein 20 to 60 mol percent of the acidic component of the alkyd resin is the aliphatic dicarboxylic acid.

5. A coated conductor according to claim 4 wherein the alkyl group is butyl.

6. A coated conductor according to claim 4 wherein the aliphatic dicarboxylic acid is adipic acid.

7. A coated conductor according to claim 4 wherein the alkyl group is butyl and the aliphatic dicarboxylic acid is adipic acid.

8. A coated conductor according to claim 7 wherein the dihydric alcohol is a neopentyl glycol and the polyhydric alcohol containing at least three hydroxyl groups is selected and trimethylolpropane.

9. Anelectrical conductor according to claim 1 having a Class H wire enamel coating beneath said cured mixture.

10. An electrical conductor according to claim 9 Wherein said enamel comprises a polymeric ester of a polycarboxylic acid of the group consisting of terephthalic acid and isophthalic acid and tris(-2-hydroxyethy l) isocyanurate.

11. An electrical conductor according to claim 7 having an enamel coating comprising the polymeric ester of terephthalic acid and .tris(24hydroxyethyl)isocyanurate beneath said mixture of alkyd resin and bu-tylated benzoguanam-ine-forrnaldehyde resin.

References Cited UNITED STATES PATENTS 2,454,187 11/1948 Leape (it 8.1., 260-850 5 2,991,274 7/19 1 Carlston 61 1 260850 3,039,979 6/1962 Car-lick et a1 260850 3,108,089 10/1963 Ferstandig 260-75 3,251,809 5/1966 Lockwood et a1. 26075 SAMUEL H. BLECH, Primary Examiner. MURRAY TILLMAN, Examiner.

J. C. BLEUTGE, Assistant Examiner. 

1. A COPPER ELECTRODE COATED WITH THE CURED MIXTURE OF AN INSULATING VARNISH INCLUDING (1) A CURABLE OIL-FREE ALKYD RESIN SELECTED FROM THE GROUP CONSISTING OF THE ESTERS OF REACTANTS CONSISTING ESSENTIALLY OF A PLURALITY OF POLYHYDRIC ALCOHOLS WITH A MEMBER OF THE GROUP CONSISTING OF ISOPHTHALIC ACID, TEREPHTHALIC ACID AND MIXTURES OF SUCH ACIDS WITH UP TO 60% OF AN ALIPHATIC DICARBOXYLIC ACID, AT LEAST ONE OF SAID POLYHYDRIC ALCOHOLS CONTAINING ONLY TWO HYDROXYL GROUPS, THE SOLE PLYHYDRIC ALCOHOL CONTAINING ONLY 2 HYDROXYL GROUPS BEING AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF PROPYLENE GLYCOL, BUTYLENE GLYCOL, 2,2,4-TRIMETHYL PENTANEDIOL,, NEOPENTYL GLYCOL, DIETHYLENE GLYCOL, DIPROPYLENE GLYCOL, BUTANEDIOL-1,4, PENTANEDIOL-1,5 AND BUTENEDIOL-1,4 AND AT LEAST ONE OF THE POLYHYDRIC ALCOHOLS CONTAINING AT LEAST THREE HYDROXYL GROUPS THERE BEING 0.7 TO 5 MOLS OF ALCOHOL CONTAINING AT LEAST 3 HYDROXYL GROUPS FOR EACH MOL OF POLYHYDRIC ALCOHOL CONTAINING ONLY 2 HYDROXYL GROUPS AND THERE BEING 1.4-1.6 HYDROXYL GROUPS IN THE REACTING ALCOHOLS FOR CARBOXYL GROUP IN THE CARBOXYLIC ACID AND (2) FROM 5 TO 15% OF A CURABLE ALKYLATED AMINOTRIAZINE-ALDEHYDE RESIN BASED ON THE TOTAL WEIGHT OF THE ALKYD RESIN AND THE ALKYLATED AMINOTRIAZINE RESIN. 